KR20040106399A - High energy density capacitors - Google Patents

Abstract

The present invention provides a capacitor comprising an inert porous body to which a first electrically conductive layer, a second barium titanate layer and an additional electrically conductive layer are applied.

Description

High Energy Density Capacitors {HIGH ENERGY DENSITY CAPACITORS}

The present invention relates to a capacitor comprising an inert porous body, to which a first electrically conductive layer, a second barium titanate layer and an additional electrically conductive layer are applied.

Capacitors play many roles in information technology and electrical energy engineering. Recently, capacitors have been studied that have high energy density and can serve as cells or be used to meet short term high load requirements.

Electrohemica Acta 45 (2000), 2483-2498 discloses electrochemical or double layer capacitors. Also known as supercapacitors or ultracapacitors, these devices store electrical energy in two capacitors connected in series, each having an electrical double layer and ions formed between two electrodes in the electrolyte. The distance at which charge separation occurs is only a few angstroms. As the electrolyte, highly porous carbon having an internal surface area of 2,500 m 2 / g or less is used. Capacitor Equation C = E₀100 farad / cm 3 at large area A and small distance d, as indicated by E · A / d The following capacitances are possible.

Where

C is the capacitance, E ₀ is the absolute dielectric constant, E is the dielectric constant of the dielectric, A is the area of the capacitor, and d is the distance between the electrodes.

Currently, the energy density of such double layer capacitors (supercapacitors) is 3 to 7 mWW / kg or Wh / L, much lower than the energy density of conventional cells (150 to 200 mWh / kg for lithium ion cells). This is because the maximum possible voltage load is limited to about 3.5 kV by the electrochemical stability of the electrolyte.

On the other hand, there are ceramic capacitors that include a type of capacitor that operates at high pressure, that is, a dielectric based on barium titanate.

Ceramic capacitors which operate at high operating voltages and contain a barium titanate based dielectric due to the high dielectric breakdown resistance of titanate of 200 μV / 0.1 μm or less are known in the prior art. However, ceramic capacitors have a relatively low capacitance.

It is an object of the present invention to ameliorate the above mentioned disadvantages.

The inventors have found that this object is achieved by a new and improved capacitor comprising an inert porous body applied with a first electrically conductive layer, a second barium titanate layer and an additional electrically conductive layer.

The capacitor of the present invention can be manufactured as follows.

In a first step, a first electrically conductive layer can be provided to the inert porous body, and a contact can be provided to the first electrically conductive layer. A second barium titanate layer may be applied on top of the first layer, and finally another electrically conductive layer may be applied on top of the titanate layer and provide a contact. The capacitor obtained in this way can be sealed, for example encapsulated, with the exception of the electrical contacts.

Suitable porous bodies have a BET surface area of 0.1 to 20 m 2 / g. , Preferably 0.5 to 10 m 2 / g, particularly preferably 1 to 5 m 2 / g, with a pore content of 10 to 90% by volume, preferably 30 to 85% by volume, particularly preferably 50 to 80% by volume. Generally a catalyst support material, for example a metal oxide such as aluminum oxide, silicon dioxide, dioxide dioxide, with a pore size of 0.01 to 100 micrometers, preferably 0.1 to 30 micrometers, particularly preferably 1 to 10 micrometers Titanium, zirconium dioxide, chromium oxide or mixtures thereof, preferably aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide or mixtures thereof, particularly preferably aluminum oxide, zirconium dioxide or mixtures thereof, or carbides, preferably silicon carbide It is based on.

The porous body can be of any shape, for example generally annular, pellet, shaped, wagon wheel, honeycomb, preferably cubic, cylindrical, rectangular or box-shaped of any size (diameter, longest edge length). have. In the case of capacitors in the field of information technology, the size, for example, generally ranges from 1 to 10 mm 3. In the field of energy engineering, larger dimensions are needed.

In order to produce the first conductive layer on the porous body, a metal, for example copper, nickel, chromium or a mixture thereof, may be used in any layer thickness, generally 10 nm to 1,000 nm, preferably 50 nm to 500 nm, particularly preferred. Preferably, it can apply | coat to 100 micrometers-200 micrometers.

The application of the electrically conductive layer to the porous body can be carried out using all known methods, for example deposition, sputtering or electroless plating, preferably electroless plating. In electroless plating, a suitable commercial plating solution is impregnated or impregnated into the porous body and heated to a temperature below 100 ° C. to deposit the metal. After metal deposition, the liquid, usually water, can be removed at elevated temperature and, if necessary, under reduced pressure.

In addition, for example iron or nickel, the first conductive layer can be created by heating the porous body in iron carbonyl or nickel carbonyl vapor. In the case of iron, the porous body can be heated to about 150 to 200 ° C., and to 50 to 100 ° C. for nickel.

In a preferred embodiment, the porous body can be heated to an elevated temperature of 50 to 100 ° C. in an inert atmosphere (eg nitrogen or argon) to produce a homogeneous metal layer. By impregnation with a similarly suitable liquid (see above), it may be advantageous to apply a crystallization nucleus, for example a nucleus of a platinum metal substrate.

Finally, a contact can be provided to the first metal layer. This can be done, for example, by brazing a metal foil on a metal-coated porous body region (preparation of a first electrode).

The dielectric may then be applied on top of the electrode initially produced. This is advantageously done using a dispersion of crystalline titanate particles of less than 10 nm in size in alcohol. The dispersion may be prepared by reacting titanium alkoxide with barium hydroxide or strontium hydroxide in an alcoholic solution, as described in German Application No. 102 21 499.9 (O.Z. 0050/53537).

After permeating or impregnating the dispersion, which may contain 5 to 60% by weight, preferably 10 to 40% by weight, of the titanate particles, the temperature is 30 to 100 ° C, preferably 50 to 80 ° C. And, if necessary, the ambient pressure can be reduced to remove alcohol to deposit titanium particles on the first electrode.

To produce a homogeneous and dense dielectric layer, the porous body can be heated to 700 to 1,200 ° C., preferably 900 to 1,100 ° C., in an inert gas atmosphere to sinter the titanate particles together to form a dense film.

To increase the layer thickness, impregnation and sintering with titanate dispersion can be repeated several times. The layer thickness is generally 10 to 1,000 nm, preferably 20 to 500 nm and particularly preferably 100 to 300 nm.

Finally, the second electrode layer can be applied in a manner similar to that used for the first electrode layer.

After applying the second electrode layer, a contact can be provided on a surface opposite the first contact to create a capacitor. Capacitors can be encapsulated encapsulated for protection and insulation purposes.

The capacitor of the present invention is a smoothing capacitor or an energy storage capacitor or a phase transition capacitor in the field of electrical energy engineering, and is suitable as a coupling capacitor, a filter capacitor or a small energy storage capacitor in the information technology field.

The capacitor of the present invention can be illustrated as follows.

Specific surface area (BET surface area) of porous body of relative dielectric constant 5,000 to 2 m 2 / g and barium titanate layer thickness of 0.1 μm (“The Effect of Grain Size on the Dielectric Properties of Barium Titanate Ceramic”, AJ Bell and AJ Moulson , in Electrical Ceramics ", British Ceramic Proceedings No. 36, October 1985, pages 57-65) provide a capacitance of about 1 dB farad / cm 3 calculated according to the equation in page 1, rows 16 to 17. Such a capacitor may be charged to a voltage of 200 kVV, in which case its energy density is 20,000 kWW / cm 3 or about 5.5 kW kWh / l.

Claims (6)

A capacitor comprising an inert porous body applied with a first electrically conductive layer, a second barium titanate layer and an additional electrically conductive layer. The capacitor of claim 1, wherein the first electrically conductive layer, the second barium titanate layer, and an additional electrically conductive layer are applied. The capacitor according to claim 1 or 2, wherein the BET specific surface area of the inert porous body is 0.1 to 20 m 2 / g. The capacitor according to any one of claims 1 to 3, wherein the void content of the inert porous body is 10 to 90% by volume. The method of any of claims 1 to 4, comprising applying an electrically conductive layer having contacts on the inert porous body, applying a barium titanate layer thereon, and applying an electrically conductive layer having contacts thereon. Method of making a capacitor of claim. Use of capacitors as smoothing capacitors or energy storage capacitors or phase transition capacitors in electrical energy engineering, as coupling capacitors, filter capacitors or small energy storage capacitors in information technology